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Wyświetlanie 1-4 z 4
Tytuł:
Enhancement of Power Efficiency in OFDM System by SLM with Predistortion Technique
Autorzy:
Sharma, P. K.
Nagaria, R. K.
Sharma, T. N.
Powiązania:
https://bibliotekanauki.pl/articles/308396.pdf
Data publikacji:
2011
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
nonlinear HPA
OFDM
PAPR
SLM
Opis:
Orthogonal Frequency Division Multiplexing (OFDM) is considered as a strong candidate for future wireless communication because it is marked by its higher frequency multiplicity and greater immunity to multipath fading. However, the main drawback of OFDM is its high amplitude fluctuations measured by peak-to-average power ratio (PAPR), which leads to power inefficiency and requires expensive high power amplifier (HPA) with very good linearity. In this paper, we propose selected mapping (SLM) with predistortion technique to decrease the nonlinear distortion and to improve the power efficiency of the nonlinear HPA. In the proposed method SLM reduces the PAPR and improves the power efficiency, the predistorter improves the bit error rate (BER) performance of the system. The PAPR reduction is possible with SLM when compared with original OFDM. After reducing the PAPR with SLM the data goes into the HPA with and without predistorter. The BER performance curves of SLM method with or without predistorter shows that, predistorter operates more effectively in SLM method than original OFDM system. At 4 dB IBO (input backoff) the conventional method with predistorter achieves 1.8 dB SNR gain than conventional method without a predistorter and at 6 dB IBO the BER performance is towards the ideal linear amplifier. The proposed system will be evaluated for OFDM system in the presence of a nonlinear power amplifier.
Źródło:
Journal of Telecommunications and Information Technology; 2011, 4; 86-91
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Complex Signal Mapping for Improving Spectral Efficiency of Li-Fi Systems
Autorzy:
Sileh, Ibrahim K.
Abdulkafi, Ayad A.
Hussein, Mohammed K.
Hardan, Saad M.
Powiązania:
https://bibliotekanauki.pl/articles/958061.pdf
Data publikacji:
2019
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
Li-Fi
OFDM
signal mapping
PAPR
BER
Opis:
Light fidelity (Li-Fi) systems based on the orthogonal frequency division multiplexing (OFDM) scheme have gained more attention in the communications circles, as a means to provide high spectral efficiency and ensure stricter data rate requirements for visible light communication (VLC) systems. However, common OFDM schemes employ Hermitian symmetry to obtain a real-valued signal which is necessary in intensity modulation and direct detection (IM/DD) optical systems, at the expense of doubling the required bandwidth. In this paper, a novel transmission scheme for an OFDM-based Li-Fi system is proposed to tackle the issue in question. A new approach to complex signal mapping (CSM), based on the pairing function method, has been developed for Li-Fi systems. It does not require Hermitian symmetry and, hence, saves about 50% of the required bandwidth. Unlike existing OFDM-based VLC approaches, the proposed scheme employs CSM to ensure a real and positive signal without Hermitian symmetry in order to fully utilize the bandwidth available to Li-Fi networks. Simulation results show that the proposed scheme significantly outperforms other systems in terms of spectral efficiency. The CSM-OFDM based Li-Fi system also achieves a good peak-to-average power ratio (PAPR) reduction with acceptable bit-error-rate (BER) performance, compared to conventional approaches.
Źródło:
Journal of Telecommunications and Information Technology; 2019, 3; 58-62
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of traffic performance of QPSK and 16-QAM modulation techniques for OFDM system
Autorzy:
Islam, I.
Hossain, S.
Powiązania:
https://bibliotekanauki.pl/articles/308854.pdf
Data publikacji:
2005
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
OFDM
QPSK
16-QAM
IFFT
frequency spectrum
PAPR
BER
Opis:
Orthogonal frequency division multiplexing (OFDM) provides better spectral efficiency than frequency division multiplexing (FDM), while maintaining orthogonal relation between carriers; hence traffic is better carried by OFDM than FDM within the same spectrum. This paper reveals a comparison of spectral efficiency, performance of communication system in context of bit error rate (BER) for the same information rate and peak to average power ratio (PAPR) of quadrature amplitude shift keying (QPSK) and 16-quadrature amplitude modulation (16-QAM) technique.
Źródło:
Journal of Telecommunications and Information Technology; 2005, 1; 147-152
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interleaving Technique Implementation to Reduce PAPR of OFDM Signal in Presence of Nonlinear Amplification with Memory Effects
Autorzy:
Aimer, Y.
Bouazza, B. S.
Bachir, S.
Duvanaud, C.
Powiązania:
https://bibliotekanauki.pl/articles/309197.pdf
Data publikacji:
2018
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
downward compatibility
interleaving technique
interleaver key
OFDM systems
PAPR reduction
Opis:
In OFDM systems, peak-to-average power ratio (PAPR) reduction of the signal is one of the main challenges that need to be overcome in order to use the transmitter in an efficient manner. As one of attractive techniques, interleaving can be used in PAPR reduction for multicarrier signals without spectrum distortion. In this paper, the authors propose to extend the possibilities of interleaving to improve PAPR reduction, to use a new coding of interleaver keys at the transmitter and a robust decoding procedure at the receiver. In order not to degrade the data rate, the use of null subcarriers to transmit side information to the receiver is proposed and evaluated. Simulation results in the context of the WLAN 802.11a standard in the presence of a nonlinear power amplifier model with memory, show a reduction of PAPR of approximately 5.2 dB, and an improvement of bit error rate and error vector magnitude of about 2 decades and 4% respectively, while respecting the spectral mask specification.
Źródło:
Journal of Telecommunications and Information Technology; 2018, 3; 14-22
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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